Question

Solutions containing $23$ g $HCOOH$ is/are :

• A. $46$ g of $70\%$ (w/v) $HCOOH$ $(d_{solution}=1.40g/ml)$
• B. $50$ g of $10MHCOOH(d_{solution}=1g/ml)$
• C. $50$ g of $25\%$ $\left(w/w\right)HCOOH$
• D. $46$ g of $5MHCOOH(d_{solution}=1g/ml)$

Answer 1

Answer: (A), (B)

$46$ g of $70\%$ (w/v) $HCOOH$ $(d_{solution}=1.40g/ml)$
$50$ g of $10MHCOOH(d_{solution}=1g/ml)$

Solutions containing 23 g HCOOH are solutions A and B.
The molar mass of HCOOH is $2+12+32=46g/mol$.
(A) $46gof70$% $\left[\frac{w}{v}\right]HCOOH(d_{solution}=1.40g/mL)$
46 g corresponds to $\frac{46}{1.40}=32.9mL$. It is 70% w/v.
This corresponds to $\frac{70}{100}\times 32.9=23g$.
(B) $50gof10MHCOOH(d_{solution}=1g/mL)$
The density is 1 g/mL. Thus, 50 g of solution corresponds to 50 mL. The solution is 10 M.
Hence, 50 mL of solution corresponds to $\frac{50}{1000}\times 10=0.5moles.$
This corresponds to $46\times 0.5=23g$.
(C) $50gof25$% $\left[\frac{w}{w}\right]HCOOH$
The concentration is 25% w/w.
50 g corresponds to $\frac{50\times 25}{100}=12.5g$.
(D) $46gof5MHCOOH(d_{solution}=1g/mL)$
The density is 1 g/mL. Thus, 46 g of solution corresponds to 46 mL. The solution is 5 M.
Hence, 46 mL of solution corresponds to $\frac{46}{1000}\times 5=0.23moles.$
This corresponds to $46\times 0.23=10.6g$.